From CoH Comic Index
The Lost are a group of homeless people in Paragon City. They hang around sewers and underneath road overpasses.
They were initially seen after the First Rikti Invasion of 2002. They were quickly dismissed, though, as simply addled survivors of the war that were carrying around discarded Rikti weapons. But then some began to notice that some of these vagabonds were mutating into something that was clearly not human. Through the sacrifice of some heroes, it was discovered that the Lost were somehow connected to the Rikti. What kind of a connection remains to be seen, though.
(Please see their Paragon Wiki entry for more information.)